[MODEL] [TEST] [CI] Remove hardcoded port 9250 and use ENV['TEST_CLUSTER_PORT']
[RAILS] Updated the dependencies for `elasticsearch-rails`

* Load -model from disk if available
* Remove coveralls (breaks with Rails, useless anyway)
[RAILS] Added test helper for `elasticsearch-rails`
WIP > ActiveSupport::Instrumentation support for Elasticsearch

See: http://edgeguides.rubyonrails.org/active_support_instrumentation.html

----

TODO:

* Documentation
* Publish "Model Search RESPONSE" event (took, number of results, etc.)

-----

NOTES:

https://github.com/rails/rails/blob/master/activerecord/test/cases/log_subscriber_test.rb
https://github.com/rails/rails/blob/master/actionpack/test/controller/log_subscriber_test.rb
https://github.com/rails/rails/blob/master/actionview/test/template/log_subscriber_test.rb